The present invention relates to devices, such as valves, which shut off a supply of water or other fluid in the case of an unwanted leak or the like.
There are several known devices that attempt to shut off the flow of water to a device that may potentially leak, such as a hot water heater. The purpose of these devices is to ensure that the supply of water is provided to such devices only in the case of a legitimate demand from the user. These devices also prevent or stop the flow of water in the event of a leak, so that there will be no new water introduced into the system to feed the leaking device.
An example of such a device is applicant""s own device disclosed in U.S. Pat. No. 6,021,808, which is fully incorporated herein by reference. Experimentation with such devices, however, has led to the discovery that there may be one or more instances when an unintentional xe2x80x9ctrippingxe2x80x9d of the valve can occur even though there is not a true xe2x80x9cfaultxe2x80x9d condition. Such a situation is often termed a xe2x80x9cnuisance callxe2x80x9d in the industry.
One manner in which such an unwanted fault can occur is when there is a significant pressure difference between the input and the output side of the valve. This can occur due to many reasons. For example, it may occur due to the fact that the output of the device, that is the side on the hot water tank, was filled during a time when the inlet water pressure was substantially lower. If the inlet water pressure rises some 10, 20 or more pounds above the output pressure, this can trick the valve into believing that there is a fault condition, thereby maintaining the valve closed, until reset manually.
A similar condition can occur in homes or businesses using private water supplies from wells or pumps. It is well known that water systems with wells or pump water experience significant fluctuations in water pressure. These fluctuations are due to the fact that the water pressure must drop low enough to trigger the pump to run long enough to fully pressurize or charge the water system. In either case, with several of the presently designed valves, the difference in the water pressure reaches the valve control line faster then the water pressure can equalize between the input and the output sides of the valve, causing a false triggering or tripping of the valve.
Accordingly, what is needed is a system, including one or more elements that can delay or slow down the system or drawn down water pressure from reaching the control line of such devices. This delay allows the water pressures to equalize between the input and output side of the valve, essentially eliminating false trigger conditions.
An additional concern with such devices is the thermal expansion and contraction, which occurs as a device to be protected, such as a water heater, heats water and shuts off. As is well known, heated water expands, while water contracts as it cools. Without a mechanism to control or account for the expansion and contraction of water, a device meant to prevent excess water leakage due to an unwanted event such as a leak will not work consistently well. Accordingly, another aspect of the present invention is to provide for and allow thermal expansion and contraction of water when used with a heating device such as hot water heater.
In accordance with one aspect of the present invention, a fluid supply shut off valve system is used with a device to be protected. The system comprises a fluid monitoring device including a shut off valve, a main input, a main output, and a pressure sensor line. The shut off valve is in a normally closed position and opens to supply fluid from the main input to the main output in response to a drop in pressure sensed by the pressure sensor line on an output side of the device to be protected. The fluid monitoring device monitors a pressure differential between the main input and the main output and causes the shut off valve to remain closed when the pressure differential reaches a predetermined amount. The system also includes a delay device coupled to the pressure sensor line. The delay device delays the response to an increase in pressure at the output side of the device to be protected.
In accordance with another aspect of the present invention, the fluid supply shut off valve system comprises the fluid monitoring device and a thermal expansion/contraction device coupled between the pressure sensor line and the output side of the device to be protected. The thermal expansion/contraction device allows contracting fluid to be drawn back into the device to be protected.
According to a further aspect of the present invention, the fluid supply shut off valve system comprises the fluid monitoring device, the delay device and the thermal expansion/contraction device.